Is Caffeinated Tea Dehydrating?

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Comparing up to six cups of caffeinated black tea a day to water, researchers study the assertion that tea acts as a diuretic, and is not as hydrating as plain water.

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For years, I’ve recommended that the healthiest beverage to drink is tea—even healthier than water, since tea has all the water of water, yet as a bonus carries a huge load of nutrition without adding calories. But: “There is a belief that caffeinated drinks, such as tea, may adversely affect hydration.” Now this was based on experiments done with high-dose caffeine pills, though, which may not entirely reflect the likely impact of tea, which is a more complex substance.

So, researchers compared four cups of black tea to four cups of water, and six cups of black tea to six cups of water. They kept volunteers locked up for 24 hours, so they could measure every drop going in, and every drop coming out.

The tests revealed no significant differences between tea and water for any of the average blood or urine measurements. It was concluded that black tea, in the amounts studied, offered similar hydrating properties to water. “Thus, tea could be considered a healthy choice of beverage.” And health professionals that don’t know any better and “incorrectly identify tea as a diuretic, could be misleading people and serve to drive consumption towards less healthy beverages.”

To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Serena.

Please consider volunteering to help out on the site.

Image thanks to ienjoysushi / flickr

For years, I’ve recommended that the healthiest beverage to drink is tea—even healthier than water, since tea has all the water of water, yet as a bonus carries a huge load of nutrition without adding calories. But: “There is a belief that caffeinated drinks, such as tea, may adversely affect hydration.” Now this was based on experiments done with high-dose caffeine pills, though, which may not entirely reflect the likely impact of tea, which is a more complex substance.

So, researchers compared four cups of black tea to four cups of water, and six cups of black tea to six cups of water. They kept volunteers locked up for 24 hours, so they could measure every drop going in, and every drop coming out.

The tests revealed no significant differences between tea and water for any of the average blood or urine measurements. It was concluded that black tea, in the amounts studied, offered similar hydrating properties to water. “Thus, tea could be considered a healthy choice of beverage.” And health professionals that don’t know any better and “incorrectly identify tea as a diuretic, could be misleading people and serve to drive consumption towards less healthy beverages.”

To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Serena.

Please consider volunteering to help out on the site.

Image thanks to ienjoysushi / flickr

Doctor's Note

This is the second video of my four-part video series about the latest discoveries on tea. See Antimutagenic Activity of Green Versus White Tea also. The nutrition without calories concept refers, not surprisingly, to my video Nutrition Without Calories. For more on caffeine myths, see What About the Caffeine? For the antioxidant comparison of black tea to other teas, see Better Than Green Tea? The “less healthy beverages” line is likely an allusion to soda, about which I have a dozen videos, including Food Industry “Funding Effect”; Mercury in Corn Syrup?; Diet & Hyperactivity; and Is Sodium Benzoate Harmful? 

For more context, check out my associated blog posts: Is Caffeinated Tea Really Dehydrating? and Schoolchildren Should Drink More Water.

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